1. Field of the Invention
The invention pertains to the field of registers for reading and displaying data pertaining to goods. More particularly, the invention pertains to apparatus and methods for identifying and tracking picked goods on a pallet conveyance using RF identification transponders (RFID tags) associated with the goods.
2. Description of Related Art
Pallets are a cost effective means used to ship products from the point of manufacture to distribution centers and finally to retailers where the merchandise is sold to the general public. Retailers need to know what goods are in the supply chain in order to make better business decisions and to make sure that goods are on the store shelves when consumers want to purchase them. Mandates from major retailers such as Wal-Mart, Target, Best Buy, Metro, and others are requiring that cases, cartons, and shipping totes, primarily shipped on pallets (hereinafter, simply “cases”), have Radio Frequency Identification transponders, commonly called “RFID tags” attached to identify the product content.
Manufacturers and distribution centers receive orders from stores for a variety of merchandise. The order is typically “picked” which means that a manufacturer or distribution center uses a pallet that is carried on the forks of a pallet conveyance, which may be a forklift truck, motorized pallet jack, manual pallet jack, or other such vehicle, onto which goods from a “pick list” are loaded for delivery to a given location. The operator will move the pallet via the conveyance to an area of the warehouse where merchandise listed on the pick list is stored. The operator will then add the number of cases listed on the pick list to the pallet. This pallet will now be called the “picked pallet”, and the goods “picked goods”.
The manufacturer or the distribution center would like to know that the right merchandise was loaded onto the picked pallet. Prior art used barcodes read with a handheld barcode scanner as a way to insure accuracy. As each item is added to the picked pallet, the barcode printed on the case is scanned with a hand held scanner. A computer system is used to check that the right merchandise was picked. This process is time consuming and depends on the operator to manually scan each case.
Prior art, such as U.S. Pat. No. 6,669,089, describes methods of reading an RFID tag on one or more pallets loaded on the forks of the forklifts. The patent does not address a method of reading RFID tags on individual cases loaded onto pallets. The antennas in this patent are fixed to the forklift structure (either to the moving fork structure, or the fixed vertical support), and are not independently movable apart from the normal raising and lowering of the forks.
Reading the RFID tags attached to cases as they are loaded onto a picked pallet has proven to be difficult using prior art. The operator can park the forklift or other pallet conveyance vehicle with the picked pallet anywhere in the warehouse. Because the RF field generated by the RFID reader and antenna is imprecise and may bounce off metallic objects in the warehouse, such as the metal shelves, it is difficult to know if the item is on the picked pallet or near it. As goods are loaded onto the picked pallet, antennas that were visible before are now covered with merchandise. Depending on the type of merchandise, the RF signal from the reader will become blocked and no additional RFID tag reading will take place.
Published Patent Application no. 2005/0071234 describes a pallet picking operation in detail. The application makes the assumption that if there is an RFID reader it will read the tag of items placed on the pallet, but does not discuss the placement of the RFID reader antennas with respect to the RFID tags on the cases. This location and proximity between the tags and the antennas is critical if the tags are going to be read correctly—or at all. As an example, paragraph 0016 states “Once on the pallet the RF reader for the pallet identifies the item and logs the item into the pallet's inventory. At the same time the forklift's RF reader reads the RF tag of the item and identifies the item in the pick list”. This requires knowing the location of the antennas of the forklift RF reader, and the location of the antennas of the pallet RF reader. The forklift is a metallic structure and RF waves from the forklift may be blocked in many cases. The pallet and forklift RF readers and antennas are not described at all.